1. Technical Field
The present invention relates generally to automated overhead traveling vehicles, and more particularly to a method, system and test fixture for allowing testing and calibration of an overhead traveling vehicle.
2. Related Art
Semiconductor fabrication facilities use automation for delivery of wafers between processing stations that include bays therebetween. In one approach, wafer holding pods are delivered via a system of overhead traveling vehicles in which each vehicle is mounted to, and movable on, a rail that is positioned over the necessary load ports. Referring to FIG. 1, an illustrative overhead traveling vehicle system 10 for use in a semiconductor fabrication facility is shown. System 10 includes at least one and, in most cases, a plurality of overhead traveling vehicles 14. Each vehicle 14 includes a main body 16 movably engaged with an elevated rail 18, and including a servomotor(s) 20 for driving a wheel(s) (not shown) for moving main body 16 along elevated rail 18. Main body 16 provides a base point 22 from which hoisting of an object may occur. Elevated rail 18 may be supported in a variety of ways such as being hung from a ceiling of the facility or supported on poles. System 10 may also include a controller 24 for controlling a plurality of overhead traveling vehicles 14 in the semiconductor fabrication facility. Tracking of overhead traveling vehicles 14 may be conducted via one or more optical sensors (not shown) that interact with a reflective tape (not shown) on rail 18.
As with any automated device, vehicles must be periodically taken out of service for repair and other maintenance, and temporarily swapped or replaced with a second vehicle. Typically each facility has an automation system that has been implemented over time such that vehicles do not always have mechanical and electrical uniformity. Accordingly, when a problem vehicle is replaced by a second vehicle, the calibration data for the problem vehicle oftentimes is incompatible with the second vehicle. Accordingly, the second vehicle malfunctions, or worse is inoperable. The reasons for this situation vary, e.g., different vehicle age, models, components, etc. One example malfunction is non-synchronization of drive servomotors for wheels of the second vehicle, which may result in dangerous operation of the vehicle. Conventionally, system operators would simply accept the malfunction or make estimated corrections to the second vehicle to minimize the malfunction.
In view of the foregoing, there is a need in the art for a method, system and test fixture for allowing testing and calibration of overhead traveling vehicles.